The invention relates to an arrangement including an object made at least partially of metal and/or precious metal and an RFID identification device, which can be used in various technological areas for identifying and tracking objects and/or carriers.
As for the objects, it concerns the use in the security sector, the logistics sector, protection against theft, in the car sector, and generally everywhere where it involves the identification and tracking of objects, parts, subassemblies, containers and so forth. Examples of this are access cards, such as chip cards, credit cards, transponder cards, telephone cards, entry cards, but also any other, relatively high-value objects in the form of valuables and works of art, unique items and suchlike, as well as technical objects such as frame/racks, vehicles and aircraft as well as their parts, also spare parts, weapons of all kinds, defense equipments, containers, any industrial parts etc. Such objects are made for example of metal, precious metal, aluminium, cast aluminium, steel, sheet metal and similar conductive materials in any shape, quality and application, the identification device being disposed on or beneath the surface of the object, e.g. in the form of inlays.
Conventional access cards as a rule comprise a plate-shaped carrier in a rectangular shape and are produced from plastic. Amongst other things, they have the advantage of straightforward and cheap manufacture, low weight and absence of electrical conductivity, but on the other hand they have the drawback that they become electrostatically charged. Furthermore, there are access cards made of metal or with a metal plating, especially of precious metal, which have the advantages of exclusivity, a valuable appearance and prestige, status symbol etc. for the user, such access cards being used in the manner of conventional cheque cards.
Conventional RFID devices comprise a stationary or mobile reading device and an electronic microchip cooperating with an aerial. The aerial and the microchip form a transponder, which receives the radio waves as soon as it comes into the region of the induction field of the aerial. The aerial, for its part, is connected to the reading device and radiates radio waves. Transponders of this kind, as so-called “smart labels” comprising a self-adhesive film or as adhesive labels, can be applied, e.g. stuck, onto the most diverse objects. Such a transponder can also be inserted or fashioned as an inlay into cards, labels or any other objects. Such RFID inlays are protected by a sheathing of plastic in order to secure them against damage.
Contactless chip cards work with transponders, which have a microchip and an aerial arrangement, and are used as cheque cards, access control cards and suchlike. The identification data, which are read out by a reading device, are stored in a memory of the chip. Modern types of transponder draw energy from HF fields, store data and send the latter back by means of attenuation modulation.
The aerial structure of conventional transponders is configured as a conductor loop and enables an inductive signal coupling. Data can be exchanged over a distance of a few centimeters by means of an evaluation device. Since the energy required by the chip can be received contactless via the conductor loop, such a transponder does not require its own voltage source.
The use of transponders with HF conductor loops causes no problems for access cards made of plastic. In the case of access cards made of metal or corresponding electrically or magnetically conductive material, eddy currents are induced in the metal surface due to the magnetic alternating flux, as a result of which a magnetic field at the metal surface is attenuated so markedly that the data transmission of the chip of the transponder is impeded. The use of a transponder with a high-frequency conductor loop directly on a metallic surface is not readily possible, since eddy currents induced in the conductor loop attenuate the magnetic field in a decisive manner. This problem can be solved by the fact that highly permeable materials, such as ferrites, are disposed and orientated between the conductor loop and the metal surface in order for the most part to eliminate eddy currents.
The shielding of high-frequency fields presents a problem in technology, which in the case of the RFID technique is caused on account of the geometry of the aerial structure disposed in the immediate vicinity of the metallic substrate. For the purpose of shielding, use is made of ferrite films which are embedded in plastic and are insulated from one another electrically. For a trouble-free operation of an RFID system in connection with a metallic environment, films are provided in the region of the transponder, which are made of a highly permeable material and suppress eddy currents which are generated by the electrically conductive surface in the aerial structure when the transponder enters into a magnetic field of a corresponding reading device. A problem addressed by the invention is to specify an identification device in connection with different objects made of metal or precious metal or metal parts, said identification device comprising an RFID system with a transponder, whereby the location and routing of the object is to be monitored or protected.